Glossary of bathing water quality terms

1976 Bathing Water Directive

This directive was introduced in 1976 to protect and improve bathing water quality, with the aim of
protecting human health and facilitating recreational use of natural waters. It was
replaced by the 2006 Bathing Waters Directive, replacing the
old three-tier classification scheme with a tighter four-tier scheme.

Abnormal situation

An event or combination of events impacting on bathing water quality
which the Environment Agency would not expect to occur, on average, more
than once every four years. During an abnormal situation water quality monitoring
is suspended until the incident is over.

Algae (seaweed and phytoplankton)

Algae are types of plant which can be very small like pinpoints floating in the sea or larger like
seaweed growing on the sea bed.

Bathing water quality

How clean a bathing water is.

Bathing water sample point

The point at a bathing water where we take water samples. This is at the place where most bathers
are expected.

Bathing water season

The bathing water season in England runs from 15 May to 30 September when we expect the
most people at bathing waters. Water quality is regularly checked during the season.

The catchment of a bathing water is the surrounding area of land where water drains into that bathing water

Coastal bathing waters

There are two types of bathing waters – coastal and inland. The directive has different standards
for these types of waters.

Colony Forming Units (cfu)

This is an estimate of the number of bacteria in a sample of water. This is done by counting the number of
colonies (groups) of bacteria growing on a filter through which the sample has been passed.

Competent authority

The organisation that has responsibility for monitoring and protecting a designated
bathing water. In England this is the Environment Agency, in Scotland the Scottish Environmental
Protection Agency, in Wales, Natural Resources Wales and in Northern Ireland, the Department of
Environment Northern Ireland

Compliance with the Bathing Water Directive

Each year, every bathing water receives a water quality classification. We measure the number of
certain types of bacteria, which may indicate the presence of pollution, mainly from
sewage or animal faeces. Escherichia coli (E.coli) and Intestinal enterococci (IE) are bacteria
that indicate the presence of faeces. An increase in the concentrations of these bacteria indicates
a decrease in water quality.

Contamination

Impurity or pollution.

Combined Storm Sewage Overflow (CSO)

Overflow pipes designed to relieve pressure on sewerage systems during periods of high rainfall, with the
aim of preventing sewage from flooding homes. Overflows allow rainwater and diluted sewage
(usually screened to remove solids), to bypass sewage treatment works and flow directly into rivers
and coastal waters.

CSO Discharge

When a CSO discharges either because of heavy rain or unexpectedly due to an incident such as a
blockage or broken pipeline.

Cyanobacteria

A type of bacteria that grow in water and get their energy from the sun, like plants. These sometimes
rapidly multiply and form blooms and scums in fresh-water that are sometimes are poisonous

Designation in England is made
by the Department of Environment Food and Rural Affairs (Defra). More information can be found
here.

Diffuse pollution

Run off from land (urban and rural) across a catchment, which can affect bathing water quality.

Discountable

Water quality samples taken during a short term pollution event can
sometimes be discounted. A pollution risk warning must have been issued and
signs displayed advising against bathing when the sample was taken. Only 15%
of samples can be removed from the classification data over a four year period.

Discounted

Samples taken during a short term pollution event which have been removed from the classification data.

Disused outfall

A pipe that is no longer used to discharge waste water.

DNA tracing technique or MST

Microbial Source Tracking (MST) is when we use DNA tracing to establish
whether pollution at a bathing water is from humans, farm animals, birds or other sources.

Effluent

Liquid waste or sewage discharged into the environment.

Emergency or storm overflow

A pipe in a sewerage system which only discharges during emergencies or when there is heavy rainfall
which can cause a risk of flooding in the sewer system.

Escherichia coli (E.coli)

E. coli are a group of organisms found in the intestines of animals and humans and survive for a
while in the environment when excreted. Many types of E. coli are not harmful but some such
as E. coli 0157, can directly cause illness. The presence of the bacteria indicates that human
or animal faeces may be present in bathing water and could contain other potentially harmful
organisms that could cause illness.

Occasionally, usually during heavy rainfall, soil containing E. coli bacteria is washed into, rivers,
streams, lakes, or groundwater leading to bathing waters, and if found, E. coli bacteria
indicates that harmful bugs could be present.

Faecal matter

Animal and bird waste.

In-season measurement

A bathing water sample taken and analysed during the bathing season.

Intestinal Enterococci (IE)

Intestinal Enterococci are found in the intestines of animals and humans although some types are
environmental in origin. The presence of the bacteria indicates that human or animal faeces
may be present in bathing water alongside other potentially harmful organisms that could cause illness.

Investigations

Investigations take place to find out the reasons for changes in water quality.

Macroalgae

Algae made up of more than one cell, such as seaweed.

Misconnections (also called wrong connections)

Misconnected sewage pipes which go directly into surface water drains are a significant source of
pollution. Misconnections can happen when domestic plumbing has been connected into surface water drains
instead of the foul sewer. This means untreated dirty water goes directly into the environment.
Find out more at ConnectRight.

Monitoring

Each bathing season we take samples at every designated
bathing water to monitor their quality. We also take a pre-season sample in early May. These are analysed
and the results are posted on the
Bathing Water Data explorer.

Not sampled

Indicates that the bathing water was closed during the bathing season, so no samples were taken.

Permit

A permit sets the standards or criteria that sewage discharge or outfalls must meet to protect water
quality

Phytoplankton

Tiny plants found in water.

Pollution

Anything that can reduce water quality, for example, sewage animal or bird faeces.

Pollution incident

Bathing water quality can be affected by pollution which may pose a risk to bathers' health.
Information on a pollution incident will be displayed on the bathing water data explorer and at the beach

Pollution risk forecast

Pollution risk forecasts are predictions that use rainfall or other factors to assess when there may
or may not be a risk of reduced bathing water quality. We can’t make these forecasts for
all bathing waters as not all are at risk from these issues.

Profile

The description of a designated bathing water and its catchment.

Sea outfall pipe

A pipe that discharges treated waste water or storm water and sewage.

Sewage

Waste water from toilets, sinks, showers and washing machines that comes from homes and businesses.

Sewage treatment works outfalls

Where the treated water comes out.

Sluice gate

Valve or gate fitted to a sluice (channel that carries a rapid current of water) to control the
rate of flow of water.

Spill frequency

The number of times an overflow discharges.

Step change

Where a significant action has been carried out to improve the bathing water quality. Data is used from the
time that the improvement took place to assess compliance, rather than a 4 year set of data.

Surface water outfall

A pipe that discharges rainwater which has fallen on the land and runs into drains and
gutters before being discharged.